It's a referral id. It basically tells Amazon who sent you; in this case "thealgorithmrepo", which is probably the folks in SkyMarshal's link below.

tracking what you clicked on to get to the product page.

does not change the page itself. If you want to have fun you can change it to "ref=monkey_poo" as I am wont to do.

So does this mean one could earn affiliate revenue from your purchases by registering as an affiliate called monkey_poo, or do they not allow you to choose your ID?

Does this mean they would get any affiliate commission if I buy the book through this link?

Seems like it would be nice to help them out.

bless the author then, to solve the mystery, the referral code is simply the one here :

http://www.cs.sunysb.edu/~skiena/#books

Thanks!

To be clear, I wasn't trying to imply anything sneaky going on. I was curious as to what these parameters mean :)

I appreciate the response

I second him. My entry "ref=kung_fu_panda" impacts a mysterious star somewhere in Messier 36.